KR20150083365A - Nonaqueous electrolyte and lithium secondary battery containing the same - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte for a high-voltage lithium secondary battery, comprising: an organic solvent in which a lithium salt is dissolved in an amount of 0.8 to 1.2 mol; (Lithium difluoro (oxalato) borate), VC (vinylene carbonate), and PS (1,3-propane sultone) as an electrolyte additive, and the lithium secondary battery can be driven at a voltage higher than 4.2 V A nonaqueous electrolyte solution capable of improving high temperature storage characteristics and high temperature cycle characteristics even when driven at a high voltage through a nonaqueous electrolyte solution for a high voltage lithium secondary battery.

Description

TECHNICAL FIELD [0001] The present invention relates to a non-aqueous electrolyte and a lithium secondary battery having the same,

The present invention relates to a nonaqueous electrolyte for a lithium secondary battery and a lithium secondary battery having the same. More particularly, the present invention relates to a nonaqueous electrolyte having improved high-temperature cycle characteristics and high-temperature storability even when a lithium secondary battery is driven at a high voltage.

As technology development and demand for mobile devices have increased, the demand for secondary batteries has increased sharply as an energy source. Many researches have been made on lithium secondary batteries having high energy density and discharge voltage among such secondary batteries, and they have also been commercialized Widely used. Further, development of an electric vehicle such as a hybrid vehicle that can solve environmental problems caused by exhaust gas of a vehicle is accelerated, and research on using a lithium secondary battery as a power source of such a vehicle is also making great progress.

The lithium secondary battery is composed of an anode, a cathode, and an electrolyte. The lithium secondary battery transfers energy while reciprocally moving both electrodes such as lithium ions from the cathode active material inserted into the anode active material, for example, carbon particles, Charge / discharge can be performed.

Lithium cobalt composite oxides, lithium nickel complex oxides, and lithium manganese composite oxides are used as the cathode active materials used in lithium secondary batteries. Of these, lithium manganese composite oxides, which are rich in resources and made of cheap manganese as a main material, are attracting attention have.

A manganese-based lithium secondary battery using a lithium manganese composite oxide as a cathode active material is used in a high voltage band through a high voltage activation in order to exhibit a high capacity. The problem of the side reaction of the active material and the electrolyte at high voltage and the problem of manganese dissolution There is a disadvantage that the battery degrades, ultimately.

Such precipitation of manganese components is more serious when stored at a high temperature because the eluted manganese component precipitates on the surface of a negative electrode active material such as a carbonaceous material and receives electrons from the negative active material to decompose the electrolyte solution in the negative electrode active material And increases the resistance of the battery. Such a problem seriously deteriorates the output, and is also a cause of inhibiting the development of a high-performance (high-output) manganese-based lithium secondary battery.

Therefore, there is a need for a lithium secondary battery using a manganese-based positive electrode active material, in which capacity reduction in a high-voltage cycle is improved and life stability is improved.

Accordingly, an object of the present invention is to provide a non-aqueous electrolyte solution for a high-voltage lithium secondary battery capable of improving high-temperature storage characteristics and high-temperature cycle characteristics when driven at a high voltage.

Another object of the present invention is to provide a lithium secondary battery which can be driven even at a high voltage and can improve high-temperature storage characteristics and high-temperature cycle characteristics when a positive electrode containing a manganese-rich cathode active material is used, And a lithium secondary battery including a non-aqueous electrolyte for a battery.

According to an aspect of the present invention, there is provided a non-aqueous electrolyte solution for a high-voltage lithium secondary battery, comprising: an organic solvent in which a lithium salt is dissolved in an amount of 0.8 to 1.2 mol; (Lithium difluoro (oxalato) borate), VC (vinylene carbonate), and PS (1,3-propane sultone) as an electrolyte additive, and the lithium secondary battery can be driven at a voltage higher than 4.2 V A nonaqueous electrolyte solution for a high-voltage lithium secondary battery.

According to a preferred embodiment of the present invention, LiODFB is added in an amount of 0.5 to 3 wt% based on the total weight of the electrolytic solution, VC is 1 to 3 wt% based on the total weight of the electrolytic solution, and PS is used in an amount of 0.5 to 2 wt% .

According to another preferred embodiment of the present invention, the electrolyte additive composed of LiODFB, VC and PS may contain 2 to 8% by weight based on the total weight of the electrolytic solution.

According to another preferred embodiment of the present invention, the lithium salt may include LIPF ₆ , and the organic solvent may be selected from the group consisting of ether, ester, amide, linear carbonate, cyclic carbonate, It can be mixed.

According to another aspect of the present invention, there is provided a lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein the positive electrode comprises a Mn-rich positive electrode active material, An organic solvent in which the salt is dissolved in an amount of from 0.8 to 1.2 mol; Wherein the lithium secondary battery is operated at a voltage of 4.2 V or higher, wherein the lithium secondary battery includes LiOHFB (lithium difluoro (oxalato) borate), VC (vinylene carbonate), and PS (1,3-propane sultone) Thereby providing a high-voltage lithium secondary battery as much as possible.

According to a preferred embodiment of the present invention, LiODFB is added in an amount of 0.5 to 3 wt% based on the total weight of the electrolytic solution, VC is 1 to 3 wt% based on the total weight of the electrolytic solution, and PS is used in an amount of 0.5 to 2 wt% .

According to another preferred embodiment of the present invention, the electrolyte additive composed of LiODFB, VC and PS may contain 2 to 8% by weight based on the total weight of the electrolytic solution.

According to a preferred embodiment of the present invention, the manganese-rich cathode active material may be represented by the following general formula (1).

Wherein M is at least one element selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V and Fe, or two or more elements simultaneously.

The non-aqueous electrolyte according to the present invention improves thermal stability and high-voltage stability and allows smooth movement of lithium ions in the electrolyte, thereby enhancing the output characteristics of the battery and ensuring the lifetime of the electrode and the electrolyte. Lt; / RTI >

More specifically, the non-aqueous electrolyte of the present invention can improve high-temperature storage characteristics and high-temperature cycle characteristics even when LiODFB, VC and PS are simultaneously added as an additive and driven at a high voltage, and the amount of gas generated from the cathode active material And the manganese dissolution is minimized, so that the phenomenon of deposition of manganese ions on the surface of the negative electrode active material can be minimized, and thus the safety and resistance characteristics of the lithium secondary battery can be improved.

Hereinafter, the present invention will be described in detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the constitutions described in the drawings are merely the most preferred embodiments, and not all of the technical ideas of the present invention are described. Therefore, various equivalents which can be substituted at the time of the present application It should be understood that variations can be made.

The present invention relates to a non-aqueous electrolyte for a high-voltage lithium secondary battery, comprising: an organic solvent in which a lithium salt is dissolved at 0.8 to 1.2 mol; And high-voltage lithium secondary batteries including lithium difluoro (oxalato) borate (LiODFB), vinylene carbonate (VC) and PS (1,3-propane sultone) as electrolytic solution additives, Thereby providing a non-aqueous electrolytic solution.

The manganese-rich cathode active material having a manganese content that is richer than the other transition metal (s) and having a layered structure is required to be driven at a high voltage to exhibit a large capacity. However, in this case, due to the side reaction with the anode, gas may be generated, and manganese and other metals may dissolve out of the anode to dissolve in the electrolyte, and then precipitate by bonding with other organic substances on the cathode. So that the durability can not be guaranteed. The present inventors have studied a method for minimizing side reactions even when driven at a high voltage in order to drive the active material at a high voltage to obtain a high capacity effect. According to this study, the inventors of the present invention found that, when LiOHFB (lithium difluoro (oxalato) borate), VC (vinylene carbonate) and PS (1,3-propane sultone) The present invention has been completed. Although it is possible to use LiODFB, VC and PS which are conventionally used for a nonaqueous electrolytic solution alone, the present invention is not limited to the use of the above additives alone but a combination of the above additives and an appropriate content range of the additives, This is a significant feature in that the conventional problem in using the lithium secondary battery is solved.

The electrolyte additive according to the present invention includes all of LiODFB (lithium difluoro (oxalato) borate), VC (vinylene carbonate) and PS (1,3-propane sultone) . Preferably, the electrolyte additive is a combination of lithium difluoro (oxalato) borate (LiODFB), vinylene carbonate (VC), and 1,3-propane sultone (PS). LiODFB contained in the electrolyte additive is represented by the following formula (2), VC is represented by the following formula (3), and PS is represented by the following formula (4). In addition, other kinds of additives may be added according to the use of the additive, and the kind and content of the additive are not limited unless the effect of the present invention other than the combination of the electrolyte additive is impaired.

LiODFB among the above additives is used as an additive differentiating from a lithium salt contained in a non-aqueous electrolyte of a lithium secondary battery. Since LiODFB used in the present invention is an additive that is not a lithium salt, it is decomposed by an oxidation- Since the passivation layer is formed on the surface of the electrolyte membrane and there is little remaining, it is contained in a relatively small amount in comparison with the lithium salt in the electrolytic solution preparation.

Preferably, LiODFB as the electrolyte additive is 0.5 to 3% by weight based on the total weight of the electrolytic solution, VC is 1 to 3% by weight based on the total weight of the electrolytic solution, and PS is 0.5 to 2% by weight based on the total weight of the electrolytic solution, LiODFB as an electrolyte additive includes 1 to 2% by weight based on the total weight of the electrolytic solution, VC is 1 to 2% by weight based on the total weight of the electrolytic solution, and PS is 0.5 to 1.5% by weight based on the total weight of the electrolytic solution. The above-mentioned content range is a range in which the formed passivation layer exhibits the performance effectively. When the content is less than the above range, the effect is insignificant. When the content is exceeded, the unit cost is increased. And then it participates in the side reaction and affects the performance of the cell. It is preferable that the content range is included.

Preferably, the electrolyte additive may consist of LiODFB, VC and PS, and the electrolyte additive consisting only of LiODFB, VC and PS may contain 2 to 8 wt%, preferably 2.5 to 4.5 wt%, based on the total weight of the electrolyte solution. have.

The nonaqueous electrolyte solution according to the present invention drives the lithium secondary battery comprising the nonaqueous electrolyte at a high voltage of not less than 4.2 V, preferably not less than 4.3 V, more preferably not less than 4.4 V, more preferably not less than 4.5 V, High temperature storage characteristics and stability of high-temperature cycle characteristics can be improved while exhibiting properties.

The non-aqueous electrolyte according to the present invention includes an organic solvent in which a lithium salt is dissolved in an amount of 0.8 to 1.2 mol, and the lithium salt is used as a lithium salt in the electrolyte solution of the present invention to exclude lithium ion mobility interference LiFF ₆ , LiFSI, LiTFSI, LiBOB, and LiOTf, which can maximize ionic conductivity, can be used alone or in combination of two or more. Any material can be used as long as it can act as a lithium salt in a lithium secondary battery. It is not limited.

The organic solvent used in the non-aqueous electrolyte of the present invention may be any of those conventionally used in an electrolyte for a lithium secondary battery without limitation, and examples thereof include ethers, esters, amides, linear carbonates, cyclic carbonates May be used alone or in combination of two or more.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate, or a mixture thereof may be included. Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, and halides thereof, or a mixture of two or more thereof. Specific examples of the linear carbonate compound include a group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate Any one selected, or a mixture of two or more thereof may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high viscosity organic solvent and dissociate the lithium salt in the electrolyte well, and dimethyl carbonate and diethyl carbonate When a low viscosity and a low dielectric constant linear carbonate are mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone, ε-caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

The nonaqueous electrolyte solution may be prepared as a lithium secondary battery by injecting the nonaqueous electrolyte solution into an electrode structure composed of a positive electrode and a negative electrode or a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process depending on the manufacturing process and required properties of the final product, and may be applied before assembling the battery or at the final stage of assembling the battery. The positive electrode, negative electrode and separator constituting the electrode structure may be those conventionally used in the production of lithium secondary batteries.

The non-aqueous electrolyte according to the present invention is more preferably used in a lithium secondary battery using a positive electrode containing a manganese-rich cathode active material. Thus, according to another aspect of the present invention, A negative electrode, and a non-aqueous electrolyte, wherein the positive electrode comprises a Mn-rich positive electrode active material, and the non-aqueous electrolyte comprises an organic solvent in which a lithium salt is dissolved in an amount of 0.8 to 1.2 mol; Wherein the lithium secondary battery is operated at a voltage of 4.2 V or higher, wherein the lithium secondary battery includes LiOHFB (lithium difluoro (oxalato) borate), VC (vinylene carbonate), and PS (1,3-propane sultone) Thereby providing a high-voltage lithium secondary battery as much as possible.

The manganese-rich cathode active material is a manganese-based cathode active material containing a large amount of manganese, for example, a compound represented by the following formula (1), but is not limited thereto.

[Chemical Formula 1]

xLi ₂ MnO ₃ (1-x) LiMO ₂

Wherein M is at least one element selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V and Fe, or two or more elements are simultaneously applied.

The xLi ₂ MnO _3. (1-x) LiMO ₂ material is a complexed material of Li ₂ MnO ₃ and LiMO ₂ , exhibiting a capacity of 240 to 250 mAh / g or more. To express such a capacity, A step is required. The present invention provides a nonaqueous electrolyte solution that minimizes side reactions even when the manganese-rich cathode active material as shown in Formula 1 is charged at a high voltage.

The positive electrode active material of the present invention can constitute a positive electrode for a lithium secondary battery together with a binder and a conductive material commonly used in the art.

The binder may be added in an amount of 1 to 30 parts by weight based on 100 parts by weight of the positive electrode active material as a component for assisting the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, But is not limited to. Specific examples of such a binder include, but are not limited to, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluorine rubber, styrene-butadiene rubber (SBR), cellulose- .

The conductive material may be added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the cathode active material, but the content thereof is not particularly limited in the present invention. Specific examples of such a conductive material are not particularly limited as long as they have electrical conductivity without causing chemical change in the battery, and for example, a carbon black conductive material such as graphite or acetylene black can be used.

Examples of the dispersion medium include N-methyl-2-pyrrolidone, diacetone alcohol, dimethylformaldehyde, propylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, isopropyl cellosolve, But are not limited to, a dispersant selected from the group consisting of butyl ketone, n-butyl acetate, cellosolve acetate, toluene, xylene, and mixtures thereof.

The above-mentioned positive electrode slurry can be coated and dried on the positive electrode current collector to form a positive electrode for a lithium secondary battery.

The positive electrode collector generally has a thickness of 10 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with carbon, nickel, titanium, silver or the like may be used.

The thickness of the positive electrode mixture slurry on the positive electrode current collector is not particularly limited, but may be, for example, 10 to 300 μm, and the loading amount of the active material may be 5 to 50 mg / cm 2.

The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein the nonaqueous electrolyte according to the present invention is used.

In addition, a cathode and a separator may be manufactured and assembled according to a conventional method known in the art to prepare a lithium secondary battery together with the anode.

As a non-limiting example of the negative electrode active material, a conventional negative electrode active material that can be used for a negative electrode of a lithium secondary battery can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium-adsorbing materials such as graphite or other carbon-based materials and the like are preferable. Non-limiting examples of cathode current collectors include foils made by copper, gold, nickel or copper alloys or combinations thereof.

As the separator, there can be used a porous polyethylene, a polyolefin film of porous polypropylene, an organic / inorganic composite separator in which a porous coating layer is formed on a porous substrate, a nonwoven film, engineering plastic, no. As a process for applying a separator to a battery, lamination, stacking and folding of a separator and an electrode are possible in addition to a general winding process.

The non-aqueous electrolyte injection according to the present invention can be performed at an appropriate stage in the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like using a can.

The lithium secondary battery according to the present invention can be used not only for a battery cell used as a power source of a small device but also for a middle or large battery module or a battery pack including a plurality of battery cells.

Preferred examples of the above medium to large devices include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Electric motorcycle including E-bike, E-scooter; Electric golf cart; Electric truck; An electric commercial vehicle, or a system for power storage, but the present invention is not limited thereto.

Hereinafter, embodiments of the present invention will be described in detail to facilitate understanding of the present invention. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the following embodiments. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Preparation of non-aqueous electrolyte

The non-aqueous electrolyte according to the present invention was prepared by adding a lithium salt-containing solution to the basic solvent shown in Table 1 to the total non-aqueous electrolyte, and adding lithium salt and LiODFB, VC and PS as additives to the total nonaqueous electrolyte in the amounts shown in Table 1 below .

Basic solvent
(volume%) Lithium salt
(weight%) additive
(weight%) EC DMC EMC LiPF ₆ LiODFB VC PS Example 1 3 4 3 One 2 One 1.5 Example 2 3 4 3 One One One 1.5 Example 3 3 4 3 One 2 One One Comparative Example 1 3 4 3 One 2 - - Comparative Example 2 3 4 3 One 2 One - Comparative Example 3 3 4 3 One 2 - 1.5 Comparative Example 4 3 4 3 One - One 1.5

The lithium secondary battery  Produce

To and mixed in a weight ratio of 3, N- _{methyl-2-pyrrolidone: 0.15Li 2 MnO 3 · 0.75LiMO 2} , a binder of polyvinylidene fluoride (PVdF) and a conductive carbon recognition 93 as the positive electrode active material: 4 To prepare a positive electrode slurry. The slurry was coated on an aluminum current collector, followed by drying and rolling to prepare a positive electrode.

Carbon black, styrene butadiene rubber (SBR) and carboxy methyl cellulose (CMC) were mixed at a weight ratio of 96: 1: 1: 2 And then dispersed in water to prepare an anode slurry. The slurry was coated on a copper current collector, followed by drying and rolling to prepare a cathode.

Thereafter, the prepared positive electrode and negative electrode were formed with an electrode assembly through a polyethylene separator, and then the electrolyte solution was injected to complete a battery.

Experimental Example

The capacity retention rate and the cell volume increase were measured by charging and discharging the lithium secondary battery obtained in Examples 1 to 3 and Comparative Examples 1 to 4 at a voltage of 4.35 V to 2.5 V and at 45 캜 for 500 cycles. Table 2 shows the results. As shown in the following Table 2, the lithium secondary batteries of the Examples had significantly higher capacity retention ratios as compared with the lithium secondary batteries of the Comparative Examples, and the increase in the cell volume was remarkably low.

In addition, after the lithium secondary batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were charged at 4.05 V and stored at 60 ° C for 8 weeks, the resistance increase rate and the cell volume increase at SOC 50 were measured, The results are shown in Table 2. As shown in the following Table 2, it was confirmed that the lithium secondary battery of the present invention had significantly lower resistance increase rate than the lithium secondary battery of the comparative example, and the increase in the cell volume was remarkably low.

4.35V-2.5V, 1C / 2C, 45C, 500cycle 4.05V, 60 ℃, 8 weeks storage Capacity retention rate (%) Cell volume increase (%) The resistance increase rate (R / R ₀ ) Cell volume increase (%) Example 1 98.1 12 1.19 8 Example 2 97.5 8 1.17 5 Example 3 96.9 10 1.10 6 Comparative Example 1 93.2 50 1.21 34 Comparative Example 2 94.3 45 1.25 29 Comparative Example 3 92.1 42 1.23 26 Comparative Example 4 85.4 18 1.33 15

Claims (8)

As a non-aqueous electrolyte for a high-voltage lithium secondary battery,
An organic solvent in which the lithium salt is dissolved in an amount of 0.8 to 1.2 mol; And
(Lithium difluoro (oxalato) borate), VC (vinylene carbonate) and PS (1,3-propane sultone) as electrolytic solution additives,
A non-aqueous electrolyte for a high-voltage lithium secondary battery capable of being driven at a lithium secondary battery voltage of 4.2 V or higher. The method according to claim 1,
Wherein the LiOHFB is 0.5 to 3 wt% based on the total weight of the electrolytic solution, VC is 1 to 3 wt% based on the total weight of the electrolytic solution, and PS is 0.5 to 2 wt% based on the total weight of the electrolytic solution. Non-aqueous electrolyte. The method according to claim 1,
Wherein the electrolyte additive comprising LiODFB, VC, and PS comprises 2 to 8 wt% based on the total weight of the electrolyte solution. The method according to claim 1,
Wherein the organic solvent is selected from the group consisting of ether, ester, amide, linear carbonate, cyclic carbonate, and the like, or a mixture of two or more thereof. A lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte,
Wherein the anode comprises a Mn-rich cathode active material,
The nonaqueous electrolyte solution may include an organic solvent in which a lithium salt is dissolved in an amount of 0.8 to 1.2 mol; And lithium ion difluoro (oxalato) borate (LiODFB), VC (vinylene carbonate) and PS (1,3-propane sultone)
Wherein the lithium secondary battery can be driven at a voltage of 4.2 V or higher. 6. The method of claim 5,
Wherein the LiOHFB is 0.5 to 3 wt% based on the total weight of the electrolytic solution, VC is 1 to 3 wt% based on the total weight of the electrolytic solution, and PS is 0.5 to 2 wt% based on the total weight of the electrolytic solution. . The method according to claim 6,
Wherein the electrolyte additive comprising LiODFB, VC, and PS comprises 2 to 8 wt% based on the total weight of the electrolyte solution. The method according to claim 6,
Wherein the manganese-rich cathode active material is represented by the following formula (1).
[Chemical Formula 1]
xLi ₂ MnO ₃ (1-x) LiMO ₂
Wherein M is at least one element selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V and Fe, or two or more elements simultaneously.